How can I manually shut down an HTTP server after displaying the access token in Go?

Manually Shutting Down HTTP Server After Displaying Access Token

To resolve the error encountered in shutting down the HTTP server, you can utilize the context.WithCancel function. This approach involves creating a context that can be canceled manually, allowing you to gracefully close the server.

<code class="go">package main

import (
    "context"
    "fmt"
    "io"
    "log"
    "net/http"
    "time"
)

var client_id = "my_client_id"
var client_secret = "my_client_secret"
var redirect_url = "http://localhost:8000/instagram/callback"

func main() {
    ctx, cancel := context.WithCancel(context.Background())

    srv := startHttpServer(ctx)

    openbrowser(fmt.Sprintf("https://api.instagram.com/oauth/authorize/?client_id=%v&amp;redirect_uri=%v&amp;response_type=code&quot;, client_id, redirect_url))

    // Listen for context cancellation signals
    go func() {
        <-ctx.Done()

        // Gracefully shut down the server
        if err := srv.Shutdown(context.Background()); err != nil {
            panic(err) // failure/timeout shutting down the server gracefully
        }
    }()

    time.Sleep(20 * time.Second)
    cancel()
}

func showTokenToUser(w http.ResponseWriter, r *http.Request) {
    io.WriteString(w, fmt.Sprintf("Your access token is: %v", r.URL.Query().Get("code")))
}

func startHttpServer(ctx context.Context) *http.Server {
    srv := &http.Server{Addr: ":8000"}

    http.HandleFunc("/instagram/callback", showTokenToUser)
    http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
        io.WriteString(w, "Hello world!")
    })

    go func() {
        if err := srv.ListenAndServe(); err != http.ErrServerClosed {
            // cannot panic, because this probably is an intentional close
            log.Fatalf("Httpserver: ListenAndServe() error: %s", err)
        }
    }()

    // Return the server reference for use in shutting down
    return srv
}

func openbrowser(url string) {
    var err error

    switch runtime.GOOS {
    case "linux":
        err = exec.Command("xdg-open", url).Start()
    case "windows":
        err = exec.Command("rundll32", "url.dll,FileProtocolHandler", url).Start()
    case "darwin":
        err = exec.Command("open", url).Start()
    default:
        err = fmt.Errorf("unsupported platform")
    }
    if err != nil {
        log.Fatal(err)
    }
}</code>

This solution utilizes a separate goroutine to handle the context cancellation and graceful server shutdown. When the user accesses the /quit route, the context is canceled, which triggers the server shutdown process.

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